I am afraid I am having trouble keeping up with the new posts, much less going back to read the older ones, but I will provide a few more comments from my perspective.
I don’t think BT.1886 graded content will be “perfect” on an sRGB display in the sRGB viewing environment, just reasonable. The straight line part of the sRGB EOTF was to avoid extreme slope, which caused problems in some color management systems. It also partly addresses the difference between the expected black point of 0.1 nit for 1886 and 0.2 nit for sRGB (with more veiling glare because of the higher ambient).
I tried for 25 years to get agreement to clarify the sRGB standard, but was always met with strong resistance. At this point it is out of my hands.
While it is true that many people assume a zero display black with BT.1886, it is only recently that this can be approximately true. Otherwise this assumption causes problems with clipping or elevation of black values when going between black-relative colorimetry and regular colorimetry.
Yes, what happened is most people sort of de-facto agreed to use black relative colorimetry, i.e. the black signal level is mapped to the display black and the 2.4 gamma is used. However, this EOTF only matches the BT1886 EOTF when the display black point is zero. The 1886 EOTF more accurately fits the mastering display measurements on which it is based. One can argue that the black-relative fixed 2.4 gamma EOTF is better at mapping the black than the 1886 EOTF, but it did not match what displays at the time were actually doing.
If you don’t like what a standard prescribes, you are free to do something different, maybe even something better, but in that case it is better to say what you are doing than to claim you are following a standard when you are not, even if most people are doing the same. Doing that causes us to have to spend time on these discussions, and in some cases inhibits progress.